JP2008288071A - Magnetic proximity switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic proximity switch in which a sensor can be made smaller and control of an impressed magnetic field can be made easily. <P>SOLUTION: The magnetic proximity switch 10 is provided with a semiconductor board 11 having an integrated circuit element for conducting a switching work, a magnetoresistive element 12 which is arranged on one surface of the semiconductor board 11 and has a magnetic sensing direction in surface direction, and at least a coil 13 for impressing a bias magnetic field on the magnetoresistive element 12. The coil 13, when an external magnetic field is not impressed, impresses the bias magnetic field in a surface direction where the magnetoresistive element 12 is formed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a magnetic proximity switch that can detect the approach of a magnetic material.

A sensor that detects the approach of an object, such as detection of rotation or position, uses a magnetic detection element (for example, a Hall element or a magnetoresistive element (hereinafter referred to as “MR element”)). There is. Sensors using these magnetic detection elements attach a magnet to the detection object in advance or magnetize the detection object, and when the detection object approaches the magnetic detection element, the approach of the detection object is known. (For example, see Non-Patent Document 1). In addition, as in Patent Documents 1 and 2, there is a method in which a magnet is attached to the magnetic detection element side and the position of the magnetic body is detected. The sensors described in these patent documents utilize that the magnetic field applied to the magnetic detection element side is reduced when the magnetic body approaches the magnetic detection element side.
Hall sensor (magnetic proximity switch) [online], Matsushita Electric Works, Ltd., [April 12, 2007 search], Internet <URL: http: // www. mew. co. jp / ac / download / fays / component / limit_switch / catalog / ps-j. pdf> JP-A-6-82465 Japanese Patent No. 2503481

  However, in the method of attaching a magnet to a detection object in advance or magnetizing the detection object, it takes time and effort to attach or magnetize the magnet. In addition, it is difficult to attach or magnetize the magnet with high accuracy. In addition, in a Hall sensor using a Hall element as a magnetic detection element, only the magnetic flux in the vertical direction of the chip can be captured, so that a magnet for applying a bias magnetic field becomes large.

  In a sensor using an MR element as a magnetic detection element, it is necessary to prepare a detection IC separately, which results in a large sensor. In addition, when a magnet is attached to the magnetic detection element side, there is a problem that variation in applied magnetic field is large.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a magnetic proximity switch in which a sensor can be miniaturized and an applied magnetic field can be easily controlled.

In order to solve the above problems, a semiconductor substrate including an integrated circuit element that performs a switching operation, a magnetoresistive element that is provided on one surface of the semiconductor substrate and has a magnetosensitive direction in an in-plane direction, and the magnetic The coil includes at least a coil for applying a bias magnetic field to the resistance element, and the coil applies a bias magnetic field in an in-plane direction where the magnetoresistive element is formed when no external magnetic field is applied. A magnetic proximity switch is provided.
In the magnetic proximity switch of the present invention, it is preferable that the integrated circuit element performs a switching operation by comparing an output voltage of the magnetoresistive element with a predetermined threshold value.
Moreover, it is preferable that the said integrated circuit element can set the said predetermined threshold value in multiple ways.

  According to the present invention, since the bias magnetic field is applied from the coil, the approach can be detected even with a magnetic material having no spontaneous magnetization. Further, the bias magnetic field can be changed according to the switching magnetic field of the MR element and the distance from the sensor to the object. In addition, the bias magnetic field can be applied with high accuracy. In addition, when the MR element has a plurality of outputs with different switching magnetic fields, the distance to the object can be detected in multiple stages. When the coil is made of WLP, a very thin magnetic proximity sensor can be realized.

The present invention will be described below with reference to the drawings based on the best mode.
The magnetic proximity switch of the present invention includes a semiconductor substrate having an integrated circuit element for performing a switching operation, and a magnetoresistive element (hereinafter referred to as “a magnetoresistive element” provided on one surface of the semiconductor substrate and having a magnetosensitive direction in an in-plane direction. MR element ”) and a coil for applying a bias magnetic field to the magnetoresistive element, and the coil has an in-plane direction in which the magnetoresistive element is formed when no external magnetic field is applied. A bias magnetic field is applied.

  An example of the semiconductor substrate is a silicon (Si) substrate. If an integrated circuit element is provided on the semiconductor substrate, it is not necessary to prepare a separate detection IC, and the magnetic proximity switch module can be reduced in size. The integrated circuit element preferably performs a switching operation by comparing the output voltage of the magnetoresistive element with a predetermined threshold value in order to detect a change in the magnetic field due to the detection object made of a magnetic material. If the coil is made by a wafer level package (WLP) process, it can be a very small sensor.

  The coil is used to apply a bias magnetic field to the MR element. When using a magnetic proximity switch, a bias magnetic field is applied by a coil, and when the object to be detected approaches, the magnetic flux is attracted to the object to be detected. Approach can be detected. The detection object does not need to be a magnet having spontaneous magnetization, and any magnetic material can be used. Therefore, there is no need to attach a magnet to the detection object or magnetize the detection object. Furthermore, accurate alignment between the magnet of the detection object and the MR element is not necessary. Further, since the coil is used as the bias magnetic field applying means, the bias magnetic field can be changed. Therefore, when the magnetic proximity switch has a plurality of outputs having different switching magnetic fields, it is possible to detect the distance from the detection target in multiple stages.

  The operation of the magnetic proximity switch of the present invention will be described with reference to FIGS. FIG. 1A shows a case where the detection object 2 made of a magnetic material is at a position far from the magnetic proximity switch 1 (hereinafter referred to as “position A”). FIG. 1B shows a case where the detection object 2 made of a magnetic material is in a position (hereinafter referred to as “position B”) that is moderately separated from the magnetic proximity switch 1. FIG. 1C shows a case where the detection object 2 made of a magnetic material is in a position close to the magnetic proximity switch 1 (hereinafter referred to as “position C”).

  The MR element detects a change in the magnetic field due to the bias magnetic field attracted to the detection object 2, and outputs an output voltage having a value corresponding to the amount of change. Since the integrated circuit element detects a change in the magnetic field due to the detection object made of a magnetic material, the detection object 2 is switched to the magnetic proximity switch 1 by performing a switching operation by comparing the output voltage of the MR element with a predetermined threshold value. Two signals of high level (High Level) and low level (Low Level) corresponding to whether or not a predetermined distance or more are output.

  The amount of change of the magnetic field when the detection object 2 approaches the magnetic proximity switch 1 changes according to the distance from the magnetic proximity switch 1 to the detection object 2. For example, in FIG. 1, when the detection object 2 is at the position A, the bias magnetic field applied from the coil is applied to the MR element as it is, but when the detection object 2 is at the position B, the detection object 2 is further When approaching the position C, the magnetic field applied to the MR element is reduced by attracting the bias magnetic field to the detection object 2, and the output voltage of the MR element also changes in accordance with the amount of decrease in the magnetic field.

  Therefore, by setting a plurality of predetermined threshold values as a reference to be compared with the integrated circuit element, the magnitude of the magnetic field when the output of the magnetic proximity switch 1 is switched to High or Low is changed to a plurality of types. As a result, the distance from the detection object 2 to the magnetic proximity switch 1 when the output of the magnetic proximity switch 1 is switched to High or Low can be changed in a plurality of ways.

  For example, as shown in FIG. 2A, when the magnetic field applied to the MR element is the magnitude indicated by “output 1”, if the setting is made so that the output High and Low are switched, the bias magnetic field is When it is 20G (Gauss), when the detection object 2 is at the position A, the state becomes a11 and a Low signal is output. Similarly, when the bias magnetic field is 20G and the detection target 2 is at the position B, the state shown in b11 is output, a Low signal is output, the bias magnetic field is 20G, and the detection target 2 is at the position C. Enters the state shown in c11 and outputs a High signal. When the bias magnetic field is 30 G, a Low signal is output regardless of whether the detection object 2 is in the positions A, B, or C.

  Also, as shown in FIG. 2B, when the magnetic field applied to the MR element is the magnitude indicated by “output 2”, if the setting is made so that the output high and low are switched, the bias magnetic field is When the detection target 2 is 20 G, the detection target 2 outputs a high signal in any of the positions A, B, and C, whereas when the bias magnetic field is 30 G, the detection target 2 is positioned. When it is in A, it is in the state shown in a22 and outputs a Low signal, and when the detection object 2 is in position B, it is in the state shown in b22 and outputs a High signal, and the detection object 2 Is at position C, the state shown in c22 is output and a High signal is output.

  Table 1 summarizes the changes in the above states.

  Therefore, when a 20 G bias magnetic field is applied while setting the output High and Low to be switched when the magnetic field applied to the MR element has the magnitude indicated by “output 1”, the position A and the position B are distinguished. Although it is not possible, it becomes possible to distinguish whether it is in position C or not. When the magnetic field applied to the MR element is the magnitude indicated by “output 2” and the setting is made so that the output High and Low are switched, and the bias magnetic field of 30 G is applied, the position B and the position C are distinguished. Although it is not possible, it becomes possible to distinguish whether it is in position A or not. By combining these two detection results, it is possible to detect the distance to the detection target in three stages of position A, position B, and position C.

  In this embodiment, in FIG. 2A, when the magnetic field applied to the MR element is smaller than the magnitude indicated by “Output 1”, the output becomes High, and the magnetic field applied to the MR element is indicated by “Output 1”. 2B, the output becomes High when the magnetic field applied to the MR element is smaller than the magnitude indicated by “Output 2” in FIG. 2B, and the magnetic field applied to the MR element becomes “Output 2”. In contrast to this, the output becomes Low when the magnitude is greater than the value indicated by “”. On the contrary, when the magnetic field applied to the MR element is the magnitude indicated by “Output 1”, the output High and Low are When setting to be switched, the output becomes High when the magnetic field applied to the MR element is larger than the magnitude indicated by “Output 1”, and the magnetic field applied to the MR element is large indicated by “Output 1”. When the output is low and the magnetic field applied to the MR element is set to be switched between High and Low when the magnetic field applied to the MR element is the magnitude indicated by “output 2”, the magnetic field applied to the MR element is “output 2”. The output may be high when the magnitude is greater than “”, and the output may be low when the magnetic field applied to the MR element is less than the magnitude indicated by “output 2”.

In order to detect the distance to the detection object in real time,
(1) A state in which a 20 G bias magnetic field is applied after setting the output High and Low to be switched when the magnetic field applied to the MR element has the magnitude indicated by “output 1”;
(2) A state in which a high and low output is switched when the magnetic field applied to the MR element has a magnitude indicated by “output 2” and a 30 G bias magnetic field is applied is a predetermined cycle. It is necessary to switch alternately. In the present invention, since the means for applying the bias magnetic field is a coil, the magnitude of the applied magnetic field can be switched easily and at high speed.

  Here, in the conventional configuration in which the integrated circuit element can set only one predetermined threshold value, the distance to the object to be detected can be determined only in two cases, that is, whether the distance is far from or near the threshold value. In the configuration of the present invention in which the element can set two predetermined threshold values, it has been shown that the distance to the detection target can be detected in three different ways. Therefore, it is clear that if the integrated circuit element can set three or more predetermined thresholds based on the same technical idea, the distance to the detection target can be distinguished and detected in four or more ways. It is.

  At this time, the magnetic proximity switch output from the integrated circuit element outputs a signal with a high voltage value when the output of the MR element is in a high level state (applied magnetic flux density is small). When the output is in a low level state (applied magnetic flux density is large), a signal with a low voltage value may be output. Conversely, when the output of the MR element is in a high level state (applied magnetic flux density is small). A signal with a low voltage value may be output, and a signal with a high voltage value may be output when the output of the MR element is in a low level state (applied magnetic flux density is large).

  Specific examples of the magnetic proximity switch of the present invention are shown in FIGS. The magnetic proximity switch of the present invention is not limited to these examples.

  A magnetic proximity switch 10 shown in FIG. 3 includes a semiconductor substrate 11 having an integrated circuit element for performing a switching operation, and a magnetoresistive element provided on one surface of the semiconductor substrate 11 and having a magnetosensitive direction in an in-plane direction. The element 12 and at least a coil 13 for applying a bias magnetic field to the magnetoresistive element 12 are provided. The coil 13 is biased in the in-plane direction in which the magnetoresistive element 12 is formed when no external magnetic field is applied. A magnetic field is applied. In this example, the applied magnetic field direction is the left-right direction of FIG. Further, the coil 13 is formed on the front surface of the semiconductor substrate 11 by the WLP process, and is provided at a position where it overlaps with the magnetoresistive element 12 in the vertical direction.

  A magnetic proximity switch 20 shown in FIG. 4 includes a semiconductor substrate 21 having an integrated circuit element that performs a switching operation, and a magnetoresistive element provided on one surface of the semiconductor substrate 21 and having a magnetosensitive direction in the in-plane direction. The element 22 and at least a coil 23 for applying a bias magnetic field to the magnetoresistive element 22 are provided, and the coil 23 is biased in the in-plane direction in which the magnetoresistive element 22 is formed when no external magnetic field is applied. A magnetic field is applied. In this example, the applied magnetic field direction is the left-right direction in FIG. The coil 23 is formed on the back surface of the semiconductor substrate 21 by a WLP process.

  A magnetic proximity switch 30 shown in FIG. 5 includes a semiconductor substrate 31 having an integrated circuit element for performing a switching operation, and a magnetoresistive element provided on one surface of the semiconductor substrate 31 and having a magnetosensitive direction in an in-plane direction. The element 32 and at least a coil 33 for applying a bias magnetic field to the magnetoresistive element 32 are provided. The coil 33 is biased in the in-plane direction in which the magnetoresistive element 32 is formed when no external magnetic field is applied. A magnetic field is applied. In this example, the applied magnetic field direction is the left-right direction in FIG. The coil 33 is formed on the front surface of the semiconductor substrate 31 by the WLP process, and is provided at a position where it does not overlap with the magnetoresistive element 32. For this reason, it is possible to provide the magnetoresistive element 32 and the coil 33 on the same plane.

  A magnetic proximity switch 40 shown in FIG. 6 includes a semiconductor substrate 41 having an integrated circuit element for performing a switching operation, and a magnetoresistive element provided on one surface of the semiconductor substrate 41 and having a magnetosensitive direction in the in-plane direction. The element 42 and at least a coil 43 for applying a bias magnetic field to the magnetoresistive element 42 are provided. The coil 43 is biased in the in-plane direction in which the magnetoresistive element 42 is formed when no external magnetic field is applied. A magnetic field is applied. In this example, the applied magnetic field direction is the left-right direction in FIG. The coil 43 is a spiral coil formed on the front surface of the semiconductor substrate 41 by the WLP process.

  A magnetic proximity switch 50 shown in FIG. 7 includes a semiconductor substrate 51 having an integrated circuit element for performing a switching operation, and a magnetoresistive element provided on one surface of the semiconductor substrate 51 and having a magnetosensitive direction in an in-plane direction. An element 52 and at least a coil 53 for applying a bias magnetic field to the magnetoresistive element 52 are provided, and the coil 53 is biased in the in-plane direction in which the magnetoresistive element 52 is formed when no external magnetic field is applied. A magnetic field is applied. In this example, the applied magnetic field direction is the left-right direction in FIG. The coil 53 is a coil (winding coil) made of a thin wire such as an enamel wire, and the semiconductor substrate 51 provided with the magnetoresistive element 52 is housed in the coil 53 (hollow part). It has become.

A magnetic proximity switch 60 shown in FIG. 8 includes a semiconductor substrate 61 having an integrated circuit element for performing a switching operation, and a magnetoresistive element provided on one surface of the semiconductor substrate 61 and having a magnetosensitive direction in the in-plane direction. The element 62 and at least a coil 63 for applying a bias magnetic field to the magnetoresistive element 62 are provided. The coil 63 is biased in the in-plane direction in which the magnetoresistive element 62 is formed when no external magnetic field is applied. A magnetic field is applied. In this example, the applied magnetic field direction is the left-right direction in FIG. The coil 63 is a coil (winding coil) made of a thin wire such as an enamel wire, and has a configuration provided on the back side of the semiconductor substrate 61.
Although not particularly shown, a configuration in which the winding coil is provided on the front side of the semiconductor substrate may be used in accordance with the example shown in FIG.

  The present invention can be used as a magnetic proximity switch that can detect the approach of a magnetic material.

(A), (B), (C) is a figure explaining operation | movement of the magnetic proximity switch of this invention. (A), (b) is a figure explaining operation | movement of the magnetic proximity switch of this invention. It is a perspective view which shows the 1st example of a magnetic proximity switch of this invention. It is a perspective view which shows the 2nd example of a magnetic proximity switch of this invention. It is a perspective view which shows the 3rd example of a magnetic proximity switch of this invention. It is a perspective view which shows the 4th example of a magnetic proximity switch of this invention. It is a perspective view which shows the 5th example of a magnetic proximity switch of this invention. It is a perspective view which shows the 6th example of a magnetic proximity switch of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Magnetic proximity switch, 2 ... Detection object 10, 20, 30, 40, 50, 60 ... Magnetic proximity switch 11, 21, 31, 41, 51, 61 ... Semiconductor substrate, 12, 22, 32, 42 , 52, 62 ... magnetoresistive elements, 13, 23, 33, 43, 53, 63 ... coils.

Claims (3)

A semiconductor substrate having an integrated circuit element for performing switching operation, a magnetoresistive element provided on one surface of the semiconductor substrate and having a magnetosensitive direction in an in-plane direction, and applying a bias magnetic field to the magnetoresistive element At least a coil for
The magnetic proximity switch according to claim 1, wherein the coil applies a bias magnetic field in an in-plane direction where the magnetoresistive element is formed when no external magnetic field is applied.   The magnetic proximity switch according to claim 1, wherein the integrated circuit element performs a switching operation by comparing an output voltage of the magnetoresistive element with a predetermined threshold value.   The magnetic proximity switch according to claim 2, wherein the integrated circuit element can set a plurality of the predetermined threshold values.

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